Tech Reports

ULCS-02-001

Value Based Argumentation Frameworks

Trevor J. M. Bench-Capon and Paul E. Dunne

Abstract

In many cases of disagreement it is impossible to demonstrate that either party is wrong. The role of argument in such cases to to
persuade rather than refute. Following Perelman, we argue that persuasion relies on a recognition that the strength of
an argument depends on the value it advances, and that whether an attack of one argument on another succeeds depends on the
comparative strength of the values advanced by the arguments. To model this we extend the standard notion of Argumentation
Frameworks (AFs) to Value Based Argumentation Frameworks (VAFs). After defining VAFs we explore their properties, proving some
results for VAFs with two values, and show how they can provide a rational basis for the acceptance or rejection of arguments,
even where this would appear to be a matter of choice in a standard AF. In particular, we show that in a VAF certain
arguments can be shown to be acceptable independent of the relative strengths of the values involved.

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